1. Field of the Invention
The present invention relates to a head suspension for a disk drive incorporated in an information processing apparatus such as a personal computer, and particularly, to a head suspension having a piezoelectric element that is attached with a nonconductive adhesive and deforms in response to a voltage applied thereto.
2. Description of Related Art
Small-sized, precision information devices are rapidly advancing, and for use with such devices, needs for micro-actuators capable of conducting positioning control for very small distances are increasing. Such micro-actuators are highly needed by, for example, optical systems for correcting focuses and inclination angles, ink jet printers for controlling ink heads, and magnetic disk drives for controlling magnetic heads.
The magnetic disk drives are strongly expected to increase their storage capacities. Increasing the storage capacity of a magnetic disk drive is generally achievable by increasing the storage capacity of each magnetic disk in the magnetic disk drive. The storage capacity or recording density of a magnetic disk will increase, without changing the diameter thereof, if the number of tracks per inch (TPI) on the magnetic disk is increased, i.e., if the width of a track is narrowed. For this, a magnetic head of a head suspension installed in the magnetic disk drive must conduct a precise positioning operation in a direction across the tracks, i.e., a sway direction. For realizing the precise positioning operation, an actuator capable of accurately moving and positioning the magnetic head in a very small section is needed.
To meet the need, the applicant of the present invention has proposed in Japanese Unexamined Patent Application Publication No. 2002-184140 a head suspension for a disk drive. The head suspension includes a base plate, a connection plate having a hinge thinner than the base plate, a load beam provided with a flexure, and a piezoelectric actuator having a pair of piezoelectric elements.
This related art employs a dual actuator system that involves, for a precise positioning purpose, a voice coil motor and the piezoelectric actuator having two piezoelectric elements made of, for example, PZT (lead zirconate titanate).
The piezoelectric actuator in the dual actuator system minutely moves a front end of the load beam in a widthwise direction (sway direction) of the head suspension. Compared with a single actuator system employing only the voice coil motor, the dual actuator system employing the voice coil motor and piezoelectric actuator is capable of more precisely positioning a magnetic head attached to a front end of the head suspension.
An important issue for the head suspension employing the dual actuator system is to protect the brittle piezoelectric elements from damage and secure electric insulation between the head suspension body and the piezoelectric elements.
One approach to address the issue is disclosed in the above-mentioned Japanese Unexamined Patent Application Publication No. 2002-184140. As mentioned above, the head suspension of this related art includes a pair of piezoelectric elements that is arranged on an actuator base connected to the load beam. The actuator base has openings in which the piezoelectric elements are fixed with an adhesive layer. The adhesive layer consists of a nonconductive adhesive and fillers. The fillers interpose between the piezoelectric elements and the actuator base to secure a clearance for electrically insulating the piezoelectric elements from the actuator base of the head suspension.
This related art is capable of surely insulating the piezoelectric elements and the actuator base from each other without damaging the piezoelectric elements.
The related art is effective to secure a minute clearance in a thickness direction when fixing the piezoelectric elements to the openings of the actuator base with the adhesive layer.
In a plane orthogonal to the thickness direction, a gap is also needed between a circumferential edge of the opening and a circumferential side face of the piezoelectric element. According to the related art, this gap must be relatively large to cover dimensional allowances of each opening and piezoelectric element, an operational error of an automatic assembling machine used to attach the piezoelectric elements to the openings, and the like.
The related art, however, takes no measures to correctly keep the gap between the circumferential edge of the opening and the circumferential side face of the piezoelectric element, properly fill the gap with a nonconductive material, and secure electric insulation between an electrode of the piezoelectric element and the actuator base.